1. Field of the Invention
The present invention relates to a technique for treating heavy hydrocarbon oil in the oil production process or oil refining process. More particularly, the present invention relates to a method and apparatus for adding and mixing a liquid phase of hydrocarbon oil to a hydrocarbon oil feedstock containing heavy hydrocarbon oil in the oil production process or oil refining process including a hydrocarbon oil dehydration process, thereby processing the heavy hydrocarbon oil to be lighter and thus increasing the throughput of the heavy hydrocarbon oil.
2. Description of Related Art
The demand for fossil fuels such as petroleum or the like keeps increasing, but oil prices are rising all over the world with the gradual depletion of oil. Particularly, as the developing countries like China, India, etc. are experiencing incremental economic growth, demands for energy and hydrocarbon oil are ever growing. In terms of supply, however, the production capacity of oil with low specific gravity has stretched to the limit or is dwindling, and the oil produced from the newly developed oil wells ever turns out to be heavier.
Petroleum (hydrocarbon oil) is classified as light, middle, heavy, or extra heavy, according to its specific gravity. The index commonly used for the specific gravity of petroleum is API (American Petroleum Institute) gravity, which is established by the API.
API gravity is a proportion of the density of oil to the density of water (60° F.). A hydrocarbon oil with relatively high API gravity is light hydrocarbon oil, and a hydrocarbon oil with relatively low API gravity is heavy hydrocarbon oil. The hydrocarbon oil having a higher API gravity displays lower viscosity and contains a larger quantity of volatile substances, while the hydrocarbon oil having a lower API gravity shows higher viscosity and contains a lower quantity of volatile substances. Hydrocarbon oil with higher API gravity is more expensive to produce.
Generally speaking, the term “light hydrocarbon oil” has an implicit meaning that the hydrocarbon oil has an API gravity greater than 30°. In an effort to fight the intensifying competition in the fields of oil refinery due to increased refinery facilities and negative profit margins, many countries around the world have adopted a method of using a large quantity of light hydrocarbon oil to dilute heavy hydrocarbon oil (with an API gravity less than 30°) that is relatively inexpensive.
This method, however, results in the reduced API gravity of the hydrocarbon oil. By the 1990's, oil production or refinery facilities had the ability to process light hydrocarbon oil having an API gravity of 35 to 40° only. Despite the recent advances in technology that allow the processing of hydrocarbon oil having an API gravity of 20 to 25°, most of the oil production or refinery facilities are designed or operated based on the hydrocarbon oil having an API gravity of 30, ending up having a limitation that the maximum proportion of heavy hydrocarbon oil blended with light hydrocarbon oil in an effort to secure the oil refinery profit is no more than 10 to 20%.
The reason of this is the increased stability of water-in-oil (W/O) emulsion produced in the hydrocarbon oil with the lower API gravity, that is, the heavier hydrocarbon oil, raising the risk of efficiency degradation, voltage loss, operational discontinuity, and so forth during the hydrocarbon oil dehydration process in the oil production or refinery facilities.
The hydrocarbon oil dehydration process can be performed in equipment like separator, coalescers, desalters, etc. For removal of water from hydrocarbon oil, the oil production facilities use separator that separate production fluids into three phases of gas, oil and water, and the oil refinery facilities basically have desalters to separate salts and moisture from hydrocarbon oil.
Desalting in the desalters is a necessary process because the salts remaining in the hydrocarbon oil can be decomposed during the distillation process and allow the formation of hydrochloric acid to accelerate corrosion or deposits in the equipment such as distillation columns, reducing the efficiency of the processing function. As the desalting process uses water to dissolve salts and adopts the basic approach to remove salts and water at the same time, it is necessary to include the oil-water separation process to remove water.
The removal of water from hydrocarbon oil is of great importance in the oil production or refinery facilities. Yet, it is difficult to eliminate water from heavy hydrocarbon oil, which is, unlike light hydrocarbon oil, has no significant difference in density from water and displays high stability of oil-in-water (O/W) or water-in-oil (W/O) emulsion.
For this reason, the hydrocarbon oil processed to be “heavier” is hard to meet the water cut that is an important parameter to evaluate the hydrocarbon oil after the dehydration process, and its high water content causes many troubles in the process and even leads to a shutdown.
In other words, there is a demand for the technique to increase the throughput of the hydrocarbon oil containing heavy hydrocarbon oil in the oil production or refinery facilities using the dehydration process by raising the proportion of heavy hydrocarbon oil blended with the relatively expensive light hydrocarbon oil and preventing a reduction of the API gravity as well.